FR2540287A1 - SEMICONDUCTOR PASTIL IMAGE DETECTION DEVICE, IN PARTICULAR FOR ELECTRONIC TUBES - Google Patents

Abstract

An image detection device which comprises a wafer of a semiconductor material having a first surface and a second surface, said first surface having a central portion which comprises a membrane, said membrane being surrounded by a rim and having a thickness more lower than that of the rim, said second surface having at least one charge storage region, and, support means for maintaining said semiconductor chip inside the device, said image detection device being characterized in that that it comprises: target retaining and retaining means 42 having a lower support element 44 which is in contact with said rim 32 of the second surface 28 of the pellet 20 near the periphery of the latter, an element of lower tension 46 having a target contact portion 52 which forcibly abuts the rim 32 of said first surface 26 of the pad, between the membrane 30 and the periphery thereof This, in order to put it under tension, and means 58 for centering and fixing the target retaining means inside the device. (CF DRAWING IN BOPI)

Description

This invention relates to an image detection device comprising

  a semiconductor chip and is more particularly aimed at a system

  improved silicon target support for such a detector device.

  It is known that image detection devices, such as silicon vidicons and silicon reinforcing tubes, utilize

  detection devices or targets which consist of mono- silicon

  The operation of such silicon targets in these devices is well known. Such an image sensing device is described in particular in US Pat. No. 4,232,245 issued Nov. 4, 1980. The silicon target described in this US Pat. comprises an input signal detection surface and a scanning surface, disposed opposite the detection surface and comprising a plurality of discrete PN-function storage diodes formed on this surface. It is common practice to thin the central portion of the detection surface of the input signal of the target, to a thickness of the order of 10 to 15, in order to obtain a high resolution and to reduce the delays or the offset The thinned target is fixed inside the device, either close to the input front plate, in the case of a silicon vidicon tube, or in the plane of the target, spaced from

  the photocathode, in a silicon reinforcing tube.

  It has been found that thinning the central portion of the target causes ripples of the thinned membrane. In some targets, the corrugations have a total amplitude of the order of 0.25 mm, which causes non-uniform variations. the focus of the output image

  and spots on this image In applications for which the

  image detection needs to provide high resolution and good

  it is necessary to reduce to a minimum or eliminate

of the target.

  U.S. Patent No. 4,103,203 discloses a thinned silicon target attached to an inner faceplate of a silicon vidicon tube using a transparent adhesive. The transparent adhesive thus used is suitable for use in tubes. vidicons in which the type of input radiation comprises photons, but it is not suitable for silicon intensifier tubes of the type described in US Pat. No. 3,761,762, or

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  photoelectrons, from the photocathode of the device's reinforcing part, are incident on the silicon target The adhesive and the glass plate prevent the electrons from striking the target A support structure or a conventional target mount, which can It can be used both in silicon vidicon tubes and in silicon reinforcing tubes is described in US Pat. No. 3,919,582. The structure described in this patent uses a ring or a support ring of a given shape, a ring of retained and an elastic washer (Belleville washer), all these elements having equal diameters, to fix the silicon target near its periphery however the target mounting structure described in this US patent was proposed for a silicon target of constant thickness without thinned central portion Such a mounting structure does not eliminate

the ripples of the target.

  An image sensing device according to the present invention comprises a semiconductor material pellet comprising a first and a second surface. The first surface has a central portion provided with a membrane. A rim surrounds the membrane whose thickness is less than that of the flange An improved support means for the device consists of target retaining means having a lower support member, in contact with the rim of the second surface of the wafer, near the periphery of the latter. the target further comprises an upper tension member having a target contact portion which abuts forcibly with the rim of the first surface of the wafer between the membrane and its periphery so as to tension the membrane. Centering means ,

  center and fix the target retaining means within the device.

  Other features and advantages of this invention will be apparent from

  the description given hereinafter with reference to the appended drawing which illustrates a

  Exemplary embodiment without any limiting character In the drawing, FIG. 1 is a longitudinal sectional view of a vidicon camera tube embodying the present invention, and FIG. 2 is a sectional view of a portion of the tube represented on FIG. the

  FIG. 1, showing the silicon target support system according to the invention.

vention.

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  FIG. 1 shows a vidicon camera tube 10 comprising an empty OUS glass envelope 12 having a transparent front plate 14,

  at one end of the envelope 12, and comprising a system of electric guns

  tronics 16, inside the envelope 12, to form an electron beam

  A photon-excitable target 20 comprising a pellet of a mono-crystalline semiconductor material is mounted on a support system 22 and is positioned near the inner surface of the faceplate 14. in order to be able to receive a light input image signal Although the target 20 is described herein as being excitable by photons, it is known to those skilled in the art that the target may also be excited by others. types of radiating input signals, for example by electrons emitted by a photocathode. A mesh electrode 24 is spaced from the target 20 in order to de-color the electron beam 18.

  the outside of the envelope 12, degmoyens (not shown) to focus manually.

  gnetically the beam 18 towards the target 20 and to bring the beam 18 to

sweep the surface of the target 20.

  Target 20, shown on a larger scale and in detail on

  FIG. 2 is constituted by a pellet of a silicon monocrystalline silicon.

  including first and second opposite major surfaces 26

  and 28, respectively The first surface 26 constitutes the detection surface

  the input signal and the second surface 28 is the scanning surface

  central portion of the first surface 26 is thinned or provided with a recess

  Conventional methods are used to obtain a membrane having a thickness of the order of 10 to 15 μm and preferably about 12 to 15 μm. A flange or edge 32 having a thickness of 30 μm. The order of 0, 127 mm surrounds the membrane 30 The second surface 28 of the target 20, which is scanned

  by the electron beam 18, comprises a plurality of photodiodes dis-

  cretes (not shown) that provide charge storage regions.

  Target 20 is of the conventional type and is described in US Pat.

No. 4,232,245 mentioned above.

  The support system according to the invention 22 comprises a ring or an-

  a target retaining bracket 34, which has an outwardly facing annular support flange 36, located in a first plane, and a

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  the outwardly extending contact flange 38, located in a second plane substantially parallel to the first support flange 36 and the contact flange 38 are connected by means of a side portion 39 which extends between The outwardly extending contact flange 38 of the target retaining support ring 34 is supported by the end wall of the casing 12 and is sealed between the casing 12 and the casing 12. front plate 14, to

  using a suitable conductive material 40, such as indium or aluminum.

  A conductive contact ring or ring 41, for example made of stainless steel, is arranged around the conductive material 40 Alternatively, if the envelope 12 is made of a ceramic material with a high alumina content instead of being made of glass the contact flange 38 can be brazed to the envelope using a known method. The target 20 is mounted in a restraint system.

  target 42 which has a lower L / 44 (and) shaped support member.

  an upper tensiom element 46, housed in the support element 44

  The outer diameter of the lower support member 48 is smaller than the inner diameter of the side portion 39 and includes a support annular portion 48 and a cylindrical skirt 50 extending substantially perpendicular to the outer edge of the annular portion 48. The target retaining ring 34 is disposed within the lower support member 44 so that the periphery of the rim or rim of the

  second surface, or scanning surface 28, in contact with the annular

  the support 48 of the lower support member.

  The upper tensioning element 46 is composed of an annular substantially planar contact portion 52 and a cylindrical wall 54, these two parts being connected by an intermediate element 56, in the form of a step. upper tension 46 being housed in the lower support member 44, the annular portion of the contact 52 of the element 46 is in

  stop on the edge of the first surface 26 of the target 20, between the mem-

  brane 30 and the periphery of the rim.

  By way of non-limiting example, a target restraint system 42 has been provided to support and energize a target 20 and to eliminate

  the folds and undulations of the membrane 30 of such a device.

  Target 20 has a nominal outside diameter of 42.93 mm.

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  annular support portion 48 of the lower annular support element 44, which is in contact with the second surface 28 of the target 20, has an internal diameter of 40, 64 mm, so as to come into contact with the second surface of the target within a distance of about 1.15 mm from the periphery of the flange 32 The annular and planar contact portion 52 of the tensioning member 46 is in contact with the first surface 26 of the target 20 , according to a ring that

  extends from a diameter of the order of 35, 56 mm to about 38, 10 nm.

  Since the second surface 28 of the target 20 is supported near the periphery of the flange 32 (a distance of the order of 1.15 mm from the outer edge of the target) and the first surface 26 of the target 20 is in contact with the periphery of the membrane 30, towards the inside of the latter, over a distance of about 2.42 mm to 3.65 mm from this periphery and is adjacent to this membrane, the target 20 can be tensioned by exerting a light force directed downwards on the upper energizing ring 46 in order to urge the target 20 to apply against the

  annular support ring 48 of the lower support member 44

  green, by exerting tension on the target 20 in the manner described above.

  above, the wrinkles or ripples that occur from the narrowed portion of the membrane 30 can be eliminated In addition, since the rim 32 of the target 20 is in contact with the first and second surfaces of different diameters as described above. above, the resonant frequency of any target vibration is increased above the value corresponding to that which exists when -the support elements

  of equal diameter ensure the fixation of the target near its periphery.

  The high-frequency vibrations are rapidly damped by

  support contacts of different diameters.

  In order to keep the target 20 energized and to complete the device

  42, the cylindrical wall portion 54 of the upper element

  2 and the cylindrical skirt 50 of the lower support member 44 are welded to each other by their circumference at a number of points. support 36 of the support ring 34 so that the second surface 28 of the target 20 is opposite the electrode mesh 24 is available a plurality

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  U-shaped centering supports 58, on the welded and oriented parts

  upwardly 50 and 54 of the target retainer 42

  58 are secured, for example by welding, to the side wall 39 of the support ring 34 in order to center and fix the target retainer 42 with respect to the target support ring 34. Although the system 22 of the invention is described above with reference to a silicon target vidicon tube, it remains understood that this system 22 can be designed to put in tension and support silicon targets in intensifier tubes of silicon and devices comprising thinned sensing elements in systems such as

  image detectors described in U.S. Patent No. 4,355,225.

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Claims (4)

  An image sensing device which comprises a wafer of a semiconductor material having a first surface and a second surface,   said first surface having a central portion which includes a mem-   brane, this membrane being surrounded by a rim and having a thickness smaller than that of the rim, said second surface having at least one charge storage region, and supporting means for holding said semiconductor wafer inside of the device, said image detection device being characterized in that it comprises: target holding and retaining means (42) having a lower support member (44), which is in contact with said flange (32) the second surface (28) of the wafer (20) near the periphery thereof, an upper tension member (46) having a target contact portion (52) forcibly abutting the rim (32); ) of said first surface (26) of the wafer, between the membrane (30) and the periphery thereof, in order to turn it on, and means (58) for   centering and securing the target retaining means within the device.   2 Image detection device according to claim 1, characterized   in that the lower support member (44) and said upper tension member   (46) are attached to each other.   An image detection device which comprises: a vacuum envelope, provided with a pellet of a mono-crystalline semiconductor material having first and second surfaces, said first surface having a recessed central portion comprising a membrane, which is surrounded by a rim, the thickness of the membrane being less than that of the rim, said second surface having a plurality of discrete regions of storage of   charge; support means for holding the pellet inside the disc   positive; an electron gun spaced from said pellet to generate a   electronic device for scanning said second surface of the wafer and a target mesh disposed between the wafer and the electron gun, the image detection device being characterized in that it comprises: a retaining ring and ring, target holder, provided with a support flange (36), located in a first plane and a contact flange (38), located in a second plane, said contact flange being 8 25 40287   supported by said casing (12) and the support and contact flanges being connected by a side wall (39) extending therebetween, a lower support member (44) having an annular ring of   support (48), with a cylindrical skirt (50) extending substantially perpendicularly   culairement to the outer edge of the annular support ring, this ring being in contact with the flange (32) of the second surface (28) of the wafer (20), near the periphery thereof, said lower support member being disposed on the support flange of the target retaining support ring, a support tension member (46) having an annular target contact portion (52) and a cylindrical wall (54), said contact portion and the wall being connected by a stepped transition portion (56), said wall being in contact with the skirt of the lower support member and being attached thereto,   the contact portion being in abutment against the rim (32) of said first   the first surface (26) of the wafer, adjacent to said membrane, and applying said wafer against the annular ring of the carrier of the lower support member, to tension said membrane and a plurality of centering and retaining supports of the targets (58) for   center and fix the lower support element and the upper tension element   higher, relative to the target support and retaining ring.